The role of upper respiratory infections in causing asthma exacerbations is well documented, and accounts for approximately 80% of childhood asthma exacerbations and hospitalizations. Rhinoviruses are the major implicated pathogens. A significant body of evidence suggests that schools are an important site of transmission of respiratory infections but little effort has gone into finding methods to decrease infectious disease transmission. The objectives of this crossover intervention study are to determine the effectiveness of three air disinfection techniques in reducing grade school children's asthma attack rates, visits to the nurse and absence rates due to respiratory infections. Upper-room ultraviolet lights, photocatalytic oxidation devices and high-efficiency filters will be installed in classrooms at a grade school in Connecticut. Airborne rhinovirus concentrations will be collected and monitored throughout the school year and analyzed using quantitative PCR methods. Absence data will be collected from the school database, and nurse's visits from the school nurse's log. Data will be modeled using advanced logistic regression models to determine effectiveness of interventions.